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Refer to the preceding subsection for an explanation of the individual fields in the header. The only difference here is that part of the data field is borrowed for the LLC header, which uses Service Access Points (SAPs) to point up to the La yer 3 protocols (see Figure

Figure 5-12. IEEE 802.3 Ethernet with 802.2 SAP Header

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Remember that IEEE SAPs differ from the Novell SAPs discussed in the preceding chapter. IEEE 80h.3 with a SAP headgr usgs £502?.:? LLC SAPs to doint to the Layer 3 protocol.

Figure 5-12 illustrates a protocol analyzer trace of an IPX ping using Novell's 802.2 frame type (Cisco's SAP eucapsulation), w hereas the preced i ng example used Novell's 802.3 (Cisco's Novell-Ether encapsu lation) frame format. The DSAP and SSAP of e0 in the LLC header point to IPX at Layer 3. If t hey were 06 instead olF e0, tluey would link to IP (see Figure 5-13). For more DSAP (destination) and SSAP (source) values, go to www.cisco.com/warp/public/473/111 12.html.

Figure 5-13. IEEE SAPS

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